One essential component of hydraulically actuated, variable valve drives that operate according to the lost-motion principle and in which a so-called hydraulic linkage with variable reducible hydraulic volume runs between the drive side, usually the cam of a camshaft, and the driven side, i.e., the gas exchange valve, there is a hydraulic valve brake that controls the set-down rate of the closing gas exchange valve independent of the cam position and limits this to specified values that are acceptable acoustically and mechanically. Hydraulic valve drives each with a hydraulic valve brake according to the class are known, for example, from U.S. Pat. No. 6,550,433 B2 and from EP 0 507 521 A1. For such a valve brake, pressure is removed from the compression chamber that becomes smaller with the closing gas exchange valve by one or more overflow openings that extend at the side of the piston in the housing wall and whose opening cross sections are reduced increasingly by a compression-chamber-side control edge of the piston entering into the housing and possibly completely closed.
Because the components of the hydraulic valve brake cannot be produced economically with arbitrarily high precision, there are still component tolerances that produce different braking characteristics even within a single manufacturing batch. However, gas exchange cycle with gas exchange valves that close at the same operating point with different stroke profiles at different crank angles with respect to the piston dead center points negatively affect the power output and emissions behavior of the internal combustion engine.